In the field of angiography, a variety of shapes and sizes of preformed catheters have been developed so that the catheter will enter the desired blood vessel once the catheter has been inserted into the vascular system of a patient. Angiographic catheters must have sufficient flexibility to follow a tortuous route into the desired position in the vascular system, but must also take on a predetermined shape once the catheter has been positioned in the vascular system so that the catheter may then be manipulated into the desired blood vessel.
Although angiographic catheters are formed having very specific shapes and sizes during the manufacturing process, the overall shape of the catheter will oftentimes change during the subsequent sterilization process and during storage of the catheter. For example, during ethylene oxide gas sterilization of an angiographic catheter, the long shaft section of the catheter will oftentimes increase in length while the preformed shape of the catheter tip will oftentimes relax. The amount of change in shape or length caused by the sterilization process or during storage of the catheter will vary between each individual catheter and therefore, it is impractical to attempt to shape the catheter during the manufacturing process to account for any subsequent change in the length or shape of the catheter caused by the sterilization process or storage of the catheter.
One approach to maintaining the desired shape of the catheter during sterilization or storage is to insert a bendable, nonresilient wire through the center of a section of catheter tubing. A physician or technician then physically bends the wire and catheter combination into the desired shape prior to sterilization. Unfortunately, there is no effective way to determine the action of the sterilizing gas on bacteria which may be located between the interior of the catheter and the stiffening wire. Additionally, the additional cost and time required by this approach makes it commercially unacceptable.
A further approach is disclosed in U.S. Pat. No. Re. 29,343 granted to Amplatz on Aug. 7, 1977. The approach disclosed in the Amplatz patent requires the use of a forming board which has a groove formed therein identical to the desired shape and length of the catheter. The cross-sectional shape of the groove is described as being wider at the bottom and narrower at the open top of the groove where it becomes a part of the flat top surface of the forming board to allow a length of thermoplastic tubing to be initially placed and retained in the groove. The forming board and catheter combination are then heated to a temperature sufficient to mold and shape the catheter to the contour of the groove in the forming board. When the forming board and catheter combination are cooled, the catheter will retain the desired shape of the groove in the forming board. Next, the forming board and catheter are placed in a sealable plastic envelope which is then sterilized and stored until the catheter is ready for use.
The forming board disclosed in the Amplatz patent does not accommodate changes in the length of the shaft section of the catheter which may occur during sterilization or storage of the catheter. If the shaft section of the catheter increases in length during sterilization or storage, the catheter tip may be forced out of the distal end of the forming board. If the shaft section of the catheter decreases in length during sterilization or storage, the catheter tip may be drawn proximally through the groove in the forming board to alter the final shape of the catheter tip.
Another approach is illustrated by a Judkins-type of catheter marketed by the Diagnostic Products Division of Mallinkrodt Inc. located in St. Louis, Mo. U.S.A. wherein a preformed catheter is placed in a plastic tray and the shaft section of the catheter is held loosely in a groove in the plastic tray. The plastic tray includes tabs molded into the top surface of the groove to retain the catheter shaft in position within the tray. There is nothing in the package to retain the catheter tip in the desired shape. Another approach to the packaging of an angiographic catheter is represented by the currently marketed femoral Judkins-type of right coronary angiographic catheter manufactured by the Cordis Corporation of Miami, Fla., U.S.A., which uses a cardboard type of support for the catheter shaft. Tabs on the cardboard support retain the shaft section of the catheter in the desired position within the package. A small plastic bag is placed on the catheter tip to maintain the desired shape of the catheter tip. In the pigtail type of angiographic catheter manufactured by the Cordis Corporation, the plastic bag is replaced by a tubular plastic sheath which requires the user to straighten the catheter tip by manually removing the catheter tip from the sheath prior to the use of this type of angiographic catheter.
The foregoing approaches do not always maintain the desired shape of the preformed catheter after sterilization or during storage of the packaged catheter. Therefore, a relatively significant number of improperly shaped catheters must be discarded or reshaped after sterilization. Additionally, improperly shaped catheters may be returned to the manufacturer by the user as being defective even though the integrity of the catheter package has been maintained.